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Forum Index : Other Stuff : Ventomobiles
| Author | Message | ||||
| Robb Senior Member  Joined: 01/08/2007 Location: AustraliaPosts: 221 |
Well we'v had velomobiles and today I stumbled on these. Ventomobiles 
They drive them straight into the wind useing the power of the wind. Seems a bit like lifting your self up in your own boots but they say they work. Well you can lift your self with a pully so it must be gearing that makes them go. |
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Tinker Guru  Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Well, it works on a boat (A NZ guy built one back in the sixties, it had a much larger propeller) so I can't see why not on a level road. On the water progress upwind was due to the huge density difference of air and water. Perhaps on land it has something to do with tyre friction? I hope they fitted 'emergency' pedals in case he drives into a wind shadow  Klaus |
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Greenbelt Guru Joined: 11/01/2009 Location: United StatesPosts: 566 |
One advantage to this design over a sail, "No tacking required, However on the downwind ,, Oh Well". Time has proven that I am blind to the Obvious, some of the above may be True? |
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| petanque don Senior Member Joined: 02/08/2006 Location: AustraliaPosts: 212 |
Seems like complicated sailing to me. Straight into the wind? I will believe it when I see it. |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
If you look at the picture, the propeller is facing in the direction of travel. So, one can safely assume the vehicle is moving straight upwind as for other wind directions the propeller would be swiveled around. The propeller set up looks wrong for a downwind unit. It is also possible the vehicle is stationary but then the motorbike behind would run into it shortly. What is not clear is if there was a direct (shaft or chain) drive to the wheels or electric drive. I guess its the latter as any mechanical connection would have too much loss from the gear train. There was a video of that catamaran boat I mentioned above on the web somewhere, I'm not sure if its still there. Klaus |
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| Greenbelt Guru Joined: 11/01/2009 Location: United StatesPosts: 566 |
A good description of the mechanics on the Ventomobile Time has proven that I am blind to the Obvious, some of the above may be True? |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Thanks for that link. The transmission is even more complicated than I imagined.. Klaus |
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MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
I remember seeing something along these lines in Popular Mechanics back in the 60's. The idea was to use "apparent wind" on an air foil similar to the one in the picture above. Sailors use apparent wind to make their crafts travel faster than the wind will 'push' them. The idea is to use forward momentum to cause wind to pass over lifting and controlling systems. This 'sucks' the craft along, much the same as using the jib sail on a sailboat to pass a swift-moving slipstream of air over the leeward side of the mainsail. This causes greater lift and thus greater 'pull' and the boat moves into the wind. The propeller would allow the thing to move directly into the wind, since it is able to use solid ground as a 'benchmark'. The comment about lifting one's self using a rope and pulley is spot on. The similarity is that there is a fixed point upon which the action created by either the rope being pulled or the prop swinging in the breeze can act upon. It's not the same as lifting yourself up with your bootstraps. I've sailed all my life and the best boat I've ever sailed close to the wind is a Capri 22. It will travel a close reach 12.5 degrees off the wind. That's nearly directly into the wind. The only thing that would go closer than that might be the velomobile in the picture above! Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| Dinges Senior Member Joined: 04/01/2008 Location: AlbaniaPosts: 510 |
I love it! Peter. |
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| Dinges Senior Member Joined: 04/01/2008 Location: AlbaniaPosts: 510 |
[quote=Robb]Well you can lift your self with a pully so it must be gearing that makes them go.[/quote] Yes and no; you can lift yourself up without a pulley too. We call that 'ropeclimbing' here ;) But yes, it's the gearing that makes it possible. Let's assume that the turbine harvests 100W of mechanical energy from the wind, with an associated drag (Fd) of 100N. This means that the wind (when exactly head-on) is exerting a force on the cart of 100N. Thus, to accelerate and achieve *any* forward speed, there must be a positive (forward) force on the cart larger than this 100N. As we know P=F*v (power [W] = Force [N] * velocity [m/s]), and as we have assumed that P=100W and F=100N, then it follows that v=1 m/s (in a forward direction). My assumed numbers are obviously not realistic as the cart can achieve much higher speeds, but it shows the basic tenet of gearing: we can trade 'force' for 'velocity' (and reverse) whilst staying within the limit imposed on us by 'power' as harvested by the turbine. Even if the drag force was very much higher (10000N ?) we could still achieve a forward speed, albeit a very small one: v=100/10000 = 0.01 m/s Obviously, reality is a bit more complicated: there are gearing losses and the hull of the cart has windresistance too; rolling resistance comes into play as we start moving. And as we speed up directly into the wind, the apparent windspeed (and hence power, and drag force) increase too). But it should still be obvious from the basic relation P=F*v that it is physically possible to travel directly into the wind by means of gearing, in effect trading speed for force to counteract the drag from wind. Peter. |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Peter, I wish my maths teacher had explained things as clearly as you 50 years ago. I'm sure my inquisitive mind would have had much more fun Klaus |
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| Robb Senior Member Joined: 01/08/2007 Location: AustraliaPosts: 221 |
After posting I was thinking that. Its more like lifting yourself with the force of gravity perhaps. Only thing is your not on the ground but in space. Could that work..... mind bends a little.... |
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| Greenbelt Guru Joined: 11/01/2009 Location: United StatesPosts: 566 |
Robb; On Earth we have a fulcrum for the force to work on. Talking about a bent Mind, I spent several years thinking about some way to move a space ship into orbit without a million tons of fire on its back end. I finally got my design together and built the strangest looking contraption you've ever seen, I plugged it in and I thought it would beat me to death before I got it unplugged. You may have guessed, it didn't work.!! It was 2 gyros mounted on a slow turning flywheel driven by a gearmotor, The Gyro motors were powered through slip rings all mounted on a wooden box. Oh! the FUN !!. Time has proven that I am blind to the Obvious, some of the above may be True? |
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